Conventionally, for example, in a lithography process for manufacturing semiconductor devices, projection exposure apparatuses of a sequential-movement-type, such as a reduction projection exposure apparatus of a step-and-repeat method (a so-called stepper) or a scanning-type projection exposure apparatus of a step-and-scan method (a so-called scanning stepper (which is also called a scanner)), are mainly used.
In the projection exposure apparatuses of this type, a wafer stage that is movable within a two-dimensional plane is provided, and a wafer is held by vacuum adsorption or electrostatic adsorption or the like, by a wafer holder fixed on the wafer stage.
While various types of the wafer holders are available, wafer holders by a pin chuck method are relatively frequently used. Further, on the wafer stage, three vertical movement pins (also referred to as center-ups or lift pins) for delivering a wafer onto the wafer holder are provided (e.g., see PTL 1). The vertical movement pins vertically move via an opening formed at the wafer holder, and receive a wafer from a carrier arm above the wafer holder and deliver the wafer onto the wafer holder by moving downward in a state of adsorbing and holding the wafer.
However, with increasing the integration degree of semiconductor devices and the size of wafers, it has come to be found that distortion that cannot be ignored occurs in the center portion of a wafer that is delivered from the vertical movement pins to the wafer holder.